1. Field of the Invention
The present invention relates to liquid crystal display devices, and more particularly relates to a technique for improving strength and visibility of small-sized display devices used for digital steel cameras and mobile phones.
2. Description of the Related Art
A liquid crystal display panel includes a TFT substrate, a counter electrode opposing the TFT substrate, and liquid crystals put between the TFT substrate and the counter substrate. The TFT substrate has thin film transistors (TFT), etc. formed thereon in a matrix form. The counter electrode has color filters, etc. formed at positions corresponding to the pixel electrodes of the TFT substrate. The liquid crystal display device forms images by controlling light transmittance of each pixel using liquid crystal molecules.
An upper polarizing plate is bonded over the counter substrate. The upper polarizing plate is formed of resin so it is easily damaged. A front window formed of glass is often disposed over the upper polarizing plate as a countermeasure. Since the front window is used for mechanically protecting the liquid crystal display panel, as show in FIG. 8, the front window is provided such that the front window and the liquid crystal display panel is spaced apart from each other.
The conventional art as shown in FIG. 8 involves a problem that a double image is observed. FIG. 8 shows a reflection type liquid crystal display panel as an example so that the problem is understood easily. In FIG. 8, after an external light L enters and transmits a front window 30, the light L is reflected at a liquid crystal display panel comprising a TFT substrate 10 and a counter substrate 20, transmits the front window 30 again, and then enters one's eyes. Incidentally, although the external light L is refracted in the front window 30, the refraction is not illustrated in FIG. 8.
A portion of the light reflected at the screen P1 of the liquid crystal display panel is reflected at the lower surface Q1 of the front window. The light travels towards the screen P2 of the liquid crystal panel and is reflected thereat. When a person visually recognizes the light reflected at P2, a phenomenon such that images are seen double occurs.
While a reflection type liquid crystal display panel was shown in FIG. 8 as an example, this also holds true for a transmission type panel. That is, in a transmission type, panel, when light transmits through the liquid crystal display panel at an angle identical with that of the light reflected at P1 in the liquid crystal display panel, the light reflects on the front window lower surface Q1 and follows the same path as described in the reflection type panel. The double image phenomenon deteriorates image quality.
On the other hand, the liquid crystal display panel involves a problem that light reflected at an end face of the TFT substrate 10 and the counter substrate 20 is emitted from the display area, thereby lowering contrast of the screen. As to solve the problem, JP-A No. 2003-5160 discloses a configuration in which an end face of the TFT substrate and the counter substrate is adapted to have a light shielding surface to prevent light reflection from the end face. However, JP-A No. 2003-5160 has no disclosure related to front windows, and no description is made for light leakage at a periphery of an image screen equipped with a front window.